Into Darkness
by Calatia
Summary: Dean finally managed to kill Abaddon, but the Mark of Cain has some unexpected side effects. He really should have listened more carefully to the warnings. My take on a possible season 9 finale. Spoilers up to and including 9x17 Mother's Little Helper. Demon!Dean.
1. Chapter 1

Alright, I have done it… I stepped over to the dark side...my first Supernatural fic...

Going to be AU as soon as the next episode airs, as I am neither clairvoyant nor a writer on the show (sadly…)

Not beta'd.

**AN:** Ok, so this is what happens when I spend too much time on tumblr after the watching the latest episode. The way Crowley said _"And now he's ready." _sounded way too foreboding and calculative to match the recovering addict that we have seen in the last episodes. I fear this will not end well. Obviously, my silly brain went off tangent with the idea and this is the result. Let me know what you think, the good, the bad, the ugly…

* * *

The alley was dimly lit and the rain from earlier was collecting in dark puddles over the broken asphalt. Dean did not give any thoughts about the scenery around him; all he cared about was the body at his feet. A body he had put here, yet he did not feel any regret or remorse. Quite the opposite. He'd finally done it, fulfilled his task that had over shadowed his life for far too long. Abaddon was dead, stabbed through the heart by the one weapon that had the power to kill her permanently.

Dean slowly turned around and stared at Crowley, the power of the Blade pulsing through his veins, fueling his anger. Killing Abaddon had heightened his reaction to the weapon, he felt like his whole being became truly one with the Blade, finally achieving its full potential. The feeling was exhilarating and Dean's skin was abuzz with the energy flowing though him. His hands gripped the Blade tightly, showing no trace of the hesitance or tremors of his earlier encounters with the weapon.

Crowley faced him calmly, hands stretched out in front of him, slowly clapping in approval.

"You have outdone yourself with this one. Excellent technique. Flawless. Cain has chosen his successor wisely."

If Dean had heard him, he did not show it. He was still in his fighting stance, slowly advancing towards the demon, eyes shining dark and murderous.

"Now, I know you feel pretty amped up right know, but you won't kill me."

"Give me one reason why not." The reply was more a growl than actual words, but Crowley understood it.

"Because you are loyal. To a fault. You see, we have grown quite close over the past months, even became friends, and if I have learned anything at all about you, then it is that you protect your friends."

"We are no friends." Again spoken in a low snarl.

"Yes, we are. And you'd better accept that, it's going to make all this sooo much easier."

"I kill you. Easy enough."

Crowley smirked and took a step towards Dean, slowly spreading his arms to his side in a gesture of surrender. "Go ahead, give it your best shot!"

Dean didn't need to be told twice. With one swift motion he swung the Blade in a perfect angle to take off Crowley's head. But the Blade refused to follow his order, instead of hitting the demon, it passed harmlessly through the air, throwing Dean completely off balance. He stumbled sideways, trying to regain his footing.

"Yeah, I thought so. You see, the power of the Blade does not only come from its bearer, it also comes from its master, Lucifer. Due to his unfortunate absence, the master of the Blade is the current ruler of Hell. Moi. And the Blade will never strike against its master." Dean struggled to understand what Crowley was talking about, partially because he couldn't believe it, but also because the annoying buzz that was pulsing in his ears, distorting all sounds.

"With Abaddon dead, there are no more disputes. I have retaken what has been mine all along. You really should have paid more attention to the fine print here. Hell must have at least one Knight at any given time. As you have just slaughtered the last Knight of Hell, the job now falls to you. And now bow before your King, my Knight."

Eyes wide with unadulterated fear, Dean fought the sudden urge that was spreading through him. His arms and legs were shaking, trying to obey the order issued by the King and at the same time held upright by the sheer willpower of a stubborn hunter. But Dean was weakened and he knew it. The fighting with Sam, the doubts, the overwhelming yearning after the Blade had worn his defenses thin over the past weeks. But a Winchester did not simply give up.

"I will not bow before you like one of your lowly demons. I am still human, and I will fight, and I will kill you."

Crowley sighted. "I really hoped you wouldn't force me to say this. Listen to me carefully Dean, the bearer of the first Blade is a Knight of Hell. And Knights of Hell are demons. That power surge you felt when you killed the bitch? That was your body shifting to its new state. Killing Abaddon turned you into what you most despised. Isn't that poetic?"

Dean's heart stopped. No, it couldn't be. Crowley was lying, he's a demon, and that's what they do, right? But he couldn't deny that he felt different, more powerful. Was this how Demons felt? He wished for the first time that Sam was here, after all, his brother had been possessed numerous times and would be able to help him.

"I – I don't believe you! You're lying." He gasped, barely able to speak coherently over the increased shivering of his body.

"Am I now? You are barely upright. Let go Dean, submit to the power inside of you and all the pain, all the struggle will be over."

Dean fell to his knees, shaking madly, but his right fist still clenched onto the boney Blade. Deciding to deliver the final push, Crowley bent down and put his hand onto Dean's head, intensifying the demonic forces cursing through the hunters mind.

"You are strong, but ever since you took on that Mark this was your destiny. Give in. Let all the anger and hatred out. Sam doesn't care about you. Castiel will soon return to heaven. They don't need you, they are even scared of you. But I value you for all your talents, take you the way you are. Be my Knight!"

"N- argh, never!" Dean collapsed on the floor in pain. He'd fought this with everything he had, but he came to realize that this might be the one fight he could not win. With one final and violent shudder Dean stilled.

Crowley smiled sadly at the motionless body in front of him. Dean Winchester was strong, but even the strongest can be taken down with the right incentive and manipulation. And Crowley prided himself to be a master in the latter. He was finally ready to return to his rightful post in hell, and his brand new Knight would play a key role in ensuring that this time, his reign would remain undisputed.

He briefly contemplated to take Dean with him right away, but ultimately decided against it. It would be so much more meaningful if his Knight would come to him on his own accord. And he would come, of that he was certain. He grabbed the first Blade out of Dean's hand and disappeared.

xxx

Sam returned from his own quest to eliminate Metatron only minutes later. Cas had given him a lift, before returning to heaven. He saw the lifeless body of Abaddon lying on the ground and rejoiced. Spotting his brother standing hunched over a few steps further down the alley, he called out.

"Dean, we did it! Metatron is dead and heaven is open for business again… Dean?" Walking closer, Sam suddenly realized that something about his brother was off. The way he held himself, the stiffness in his movements, made Sam approach more cautiously. Just as he slowed to a halt, his brother turned around and leveled his eyes with him. His shiny, large and utterly black eyes.

Sam gasped. "No! Oh no no… Dean?" He felt something cold creep up over his back, and it took him a moment to realize that it was fear.

"Hey Sammy." Dean's voice sounded mechanical, completely void of any emotion, mocking the use of the old nickname. "Guess I should have read the fine print, turns out if you kill the last Knight of Hell, you are the first in line to be the next."

"Who are you?" Sam asked in an icy voice.

"Me? Sammy, I am disappointed. You should know better."

"Get out of my brother!" Sam snapped, still concerned, but slowly calming himself. Possession he could deal with.

"Oh now that would be impossible! One hundred percent Dean Winchester, just with a dramatically increased life expectancy."

Sam blanched. The reply from his brother had just smashed any hope that he still held.

"Crowley. I'm gonna kill the bastard." Sam was livid. How dare he turn his brother into a monster? His hands automatically went for his knife and the next thing he knew was that he felt himself shoved into the wall, and held in place by an invisible force.

"Not if I can help it. Ah, please don't insult me with that poker. You know that your knife is useless against a Knight of Hell." And with a flick of his hand the knife fell out of Sam's hand. "There, that's better. You just don't understand. This is what I truly am. A killer. And Crowley takes me the way I am. With all my faults. Figured it would be a relief for you to get finally rid of me."

"Dean, no, I never meant-" Sam struggled against the demons hold on him.

"Doesn't matter anymore. Bye Sam, you are finally free to live your life the way you want to. The next time we meet, don't expect any sympathies."

"No, wait!" Sam cried out in desperation. "Just hear me out. If you are still Dean, still my brother, then please listen to me."

"Now we are brothers again? Correct me if I am wrong, but wasn't it you that said you can't trust me anymore? Fine. But be quick about it."

Sam felt the pressure that pushed him against the wall ease up slightly, not enough so he could move, but enough to allow him the breath more easily.

"I said these things because I needed you to understand that we can't keep going like this. This codependency, it needs to end. We both need to find a healthier way to live. But Dean, you are still my brother, the only family that I have left and I need you." He thought he saw the tiniest flinch in his brothers emotionless face, and that little motion gave him the courage to continue.

"I know the Mark has pulled you under for quite some time now, and I failed to do anything about it because I was too stubborn, but I am here now. Let me help you. You carried me through my addiction, the whole Lucifer disaster, saved my ass in that church and you never lost your faith in me. Now it's my turn to return the favor. Fight this, Dean, this is not you." He paused briefly, giving Dean time to process the words, and they did not fail to make an impact. So he went all in.

"You are not a killer, you are the kindest, most emphatic person I know, but you always think that you carry the weight of the world on your shoulders. You don't. You are the most amazing big brother I could ever have wished for, the finest hunter out there and a darn great guy. This isn't your fault. This isn't your weight to bear alone. Let me in. Let me help you. Please, brother."

During the last few sentences Dean had closed his eyes, head hanging low. Sam felt the force holding him falter, but it did not let go completely. When Dean raised his head, Sam let go of the breath that he had been holding since he finished his speech. The eyes that met his were a familiar green and they were swimming in unshed tears.

"Sammy… not your fault. I screwed up… I'm sorry. I'm not str-…strong enough to fight this." Dean visibly struggled to speak. Sam could see all the pain and the hardship of a life lived in constant struggle to survive, to protect in those troubled eyes. His heart went out for his brother. He had been under so much pressure, pretty much his entire life. It was no wonder that he finally cracked under it. He just wished that it hadn't been him that gave his brother the final push.

"NO! Dean, you are! If anyone is strong enough, then it's you." Sam could feel how close he was to reaching his brother, and he meant every word he said. It had been necessary for him to distance himself and find out who Sam Winchester really was, but he never meant to drive his brother into this!

"The Blade, it- it pulls me in. Can't fight the power in me. Crowley… as long as he holds the Blade, he has me, I can hear it calling…" Dean trailed off, his voice a hoarse whisper.

"Let me go and I will help you fight this. We can do this. Together!" _Damn, Dean, please, please don't give in. Please don't give up hope._

Dean simply shook his head, a lonely tear sliding down his cheek. His whole frame shook from effort and raw emotion. After what seemed like ages to Sam, Dean slowly stilled, arms hanging limb next to his lean body. When he looked up his eyes had turned back into black and his face was void of any emotion. "You can't help me. This is what I am now. It's too late." And with that he disappeared.

Left alone in the alley, Sam was in shock. Released from the hold, the tall hunter slowly slid down the wall, all strength drained out of him.

"Oh god, Dean." He choked out. "What have I done?"

* * *

**AN2:** I now this makes Dean look quite a bit weaker than he usually is. But he has been through so much this season, he lost the trust and support of Sam, has distanced himself from Cas and is pretty much convinced that he doesn't deserve anything good anyway. The Mark is adding an addiction that he can't fully control. In one word, he is vulnerable, and Crowley would totally use that.

Thanks for reading, reviews are loved!


	2. Chapter 2

**AN:** Ok, so this was supposed to be a one-shot, but all the enthusiastic reactions have prompted my brain to continue with this. Seriously, I was blown away by the amount of reviews, alerts and favorites. You guys rock!

The problem is, I usually complete my multi chapter fics before I post the first chapter, as my writing tends to be rather erratic and I edit heavily. This is the first time I'm posting a work in progress and I'm terrified… I hope I won't make too big a mess out of it!

**Warnings:** Nothing too graphic, but it gets dark and angsty!

* * *

Dean's first teleportation was a trial run and to be honest, also somewhat of an accident. He just needed to get out and went by pure instinct. Simply thinking of moving out of sight was enough, and without much effort, he found himself standing on the flat rooftop of the building he had just held Sam against. He walked over to the edge and looked down into the alley, searching out his brother. Dean stood there and watched in motionless silence until Sam finally got up, slowly stalked over to the Impala, started the car and drove off.

He knew he should be more upset by what just happened, but he couldn't find the energy to care. The world around him was blur, insignificant. He felt his old life slipping further and further away, his vision tunneling on the task at hand. Find his blade. That was all that counted. He needed it back; he needed to feel the power surge through him again. But he also knew where Crowley had taken the blade. And that was the last place he ever wanted to see again.

Dean could hear the hum of the weapon, it was a hypnotic sound and he felt it reaching out for him, calling him in. It engulfed all his senses, and his hesitation to return to hell was getting overruled. Without a conscious thought, he closed his eyes and gave himself over to the call.

If anyone had been watching him, they would have simply seen him disappear. But to Dean this was nothing like his first teleport. This time it took much longer and he could actually feel the change of environment around him. He recognized his new location immediately. He had, after all, spent nearly 40 years here, and they were hard to forget. Although this time he did not find himself in the dungeons. He looked around and what he saw resembled an elegant office, decoration completely over the top with gold ornaments covering every square millimeter of free surface, but all in all, it was very Crowley.

"Dean! I was wondering when you would drop by. Welcome to my modest lodgings." He spun around with his arms stretched out, a proud grin on his face.

Dean did not look at him. He didn't care about the room, the decoration, or the fact, that he was standing in hell. His gaze was fixed on the blade that was lying innocently on Crowley's enormous desk.

"Of course. You are here to claim what is rightfully yours. Go ahead." Dean strode over towards the desk, but was stopped by Crowley's firm hand on his chest. "Not so fast, my Knight. First we need to talk business." Dean frowned, but stopped his forward motion.

"You see, killing Abaddon was just the beginning of reclaiming my old position. She managed to create quite a large following, and once they heard of her unfortunate demise, they fled. You will find them, and you will kill them before they become a problem for me. Here is the list; they are all hiding amongst the humans. With your old and new skills, it should be easy for you to track them down."

He passed Dean a piece of paper, covered in names and locations. Dean quickly scanned the list, there had to be at least a hundred names on there.

"What about the humans they possess?"

"Do I look like the Salvation Army? Demons don't re-use vessels. Kill them. Nice and clean. And make no mistakes; I expect my orders to be followed to the letter. Now go, get your precious and then get to work!" Crowley accentuated the last three words his index finger, stabbing it into Dean's chest in sync with each syllable while he held the taller man in his scrutinizing gaze.

The newly minted knight didn't care. He didn't even notice the thinly veiled threat in Crowley's words. All he could see was the blade, lying only a few feet away from him, and suddenly he was done waiting. He roughly pushed Crowley out of the way and reached the desk with two long strides. Fingers trembling in anticipation, he reached out and grasped the handle of his weapon. The moment his fingers made contact, the now well known energy began pulsing through his veins and he felt suddenly whole again. This was it; this was all he ever needed. He barely heard Crowley's farewell before he teleported himself out of hell.

xxx

Sam drove back to the bunker in a hazy daze. The picture of his brother with his black demon eyes was on an endless repeat in his mind. This turn of events had come so sudden and unexpected that he could not grasp the full extent of it. All he knew was that he'd royally screwed up and that, as usual, his brother was paying the price for his mistakes.

Eventually Sam pulled the Impala to a stop in the parking garage of the bunker, and with a pinch of irritation realized that he had no recollection of the drive itself. He hoped that he hadn't broken too many traffic laws.

Entering their home, a wave of emptiness washed over him and for the first time since Dean's return from purgatory he felt truly and utterly alone. He walked into his brother's bedroom and breathed in the familiar scent. Sitting down on the bed, he closed his eyes and took several deep breaths, calming his frayed nerves, and allowing his mind to take back at least a little bit of control.

Once he had calmed himself down, he walked back into the library, desperate to find something, anything that would help him get his brother back. But as he saw the stacks of books they had accumulated during their research into Abaddon and the Knights of Hell he grimaced. There was no way he could do this on his own, he needed help. And so he called on the only one out there who might be able and willing to offer assistance.

"Cas? Hey man, I know you're busy, but I need your help." He slowly turned around in a circle, scanning the room for any signs of the angel. But he wasn't here. "Please. It's Dean. He's in trouble." This time he didn't even need to turn around. The familiar flutter of wings came almost immediately after he stopped. Sam suppressed an exasperated sigh. Of course the angel would come as soon as he mentioned Dean…

"What's going on Sam? Where is Dean?"

"Cas, he-" Sam hesitated, voicing it out loud made it so much more real. When he finally continued it all came out in one rush. "He's a Knight of Hell. Crowley turned him into his pet demon." There. He'd said it.

The look on Castiel's face turned from concern to disbelieve in seconds, covering anger and fear on the way. "Are you sure it's really Dean? He could be possessed."

"No Cas, I saw him. The real Dean. He was struggling against the power of the mark before he turned completely, it happened right in front of my eyes and I couldn't- I didn't…." He stopped, took a deep breath. "There was nothing I could do." He added, in a whisper so low and strained that Cas could barely hear him.

The angel remained silent, letting the full implications of Sam's words wash over him. The sudden loss of Dean caused him physical pain, but nothing on his appearance betrayed his inner agony.

Sam sat down on one of the chairs in the library, head supported by his hands. "How could we miss this? How the hell have we missed the fact that this stupid mark turns people into _demons_?"

"There is no precedence for this anywhere to be found. The only one to ever bear the mark was Cain himself, and he made a deal with Lucifer. It was never mentioned that it was the mark that turned him into a Knight of Hell. Record keeping wasn't exactly up to today's standards back then and most angels, including me, didn't really care about humans at that time. Nobody expected humanity to last this long, most of us thought it would just be a phase." At Sam's unbelieving look he added apologetically. "If it's any consolation, I'm glad that I was wrong. Unfortunately for us, that means there is virtually no information for us to find."

"Ok, let's look at this logically, what do we know? We know that Dean is a demon, that he is not possessed, and that he claims to be a Knight of Hell. This means all our usual weapons like the knife, your sword and exorcisms are useless. We can't track him, because it stands to chance that when it didn't work with Abaddon, it won't work with him either. We can't track the blade, because the only person other than Dean and Crowley who knew the spell is dead. Now you are saying that the angels have very limited knowledge on the Blade and the Mark of Cain… Cas, we got nothing to go on here!"

"Maybe we do. We have to find Cain. He is the key. He managed to walk away from hell, from being a Knight. We find him, we find a way to help Dean." The determination in his voice made it clear to Sam that he would leave no stone unturned in his quest to save his friend.

xxx

Two days later and Sam was at loss. He had read through all their research again, checked all of Dean's notes on Cain, his last known location and the spell that led him there. But the information was incomplete, and the locator spell was only mentioned, never written down in detail. Even if they had the complete spell, it would be futile, as it only pointed to the mark, and not to Cain. It could help them track Dean, but without a cure, that was of little use. The sound of the angel returning managed to pull him out of his weariness.

"Please tell me you have found something."

"I'm sorry, no. Cain has vanished. None of my sources have been able to track him. But they will keep at it."

"Dam it Cas!" Sam swiped his long arms over the table, sending all the papers tumbling to the floor. "That's not good enough. Dean is out there, doing god know what under Crowley's control. And what have we found? A big huge pile of nothing." Sam was pacing the room, arms roaming with wild gestures.

Cas stood passively in the entryway and watched the younger Winchester blow off some steam. He had something very similar before he made his way to the bunker. But they were of no use to Dean if they both lost their temper. So Cas swallowed his own despair.

"Sam…" he prompted, getting the other man's attention.

Sam whirled around as he heard his name called in a calm tone. He looked over at the angel and saw the same misery shine in those blue eyes, but Cas controlled his emotions and if he didn't know the angel so well, Sam would have missed it. He let out a deep breath and put both his hands onto the nearest table, letting his head hang low as he let go of all the anger.

"I'm sorry Cas. I know you are doing your best. I just…" he trailed off, shaking his head.

Cas walked over and put a hand on Sam's shoulder in a gesture of silent support. "I miss him too."

Sam turned his head to look at his friend, and this time he saw all the stress and agony clearly written all over Cas' face.

"I know Cas." He said in a small voice. "All this time I have tried to push him away, and now that he is gone…" he hesitated, but Cas' open face prompted him to continue. "I just want him back. You know, I once told him that if he was dying and ok with it, then I would let him go. And I would. If he wanted to quit hunting and settle down, I would let him go. I would move on. But this, this is so much worse. To know that he is out there, doing… unimaginable things… and I can't…I can't help him. Cas, I failed him." Sam was fighting the tears that threatened to escape from his eyes.

"Sam, don't give up hope. We'll find a way to get to him."

"And what if there is no cure? What if we find him and all we can do is restrain him? What if the Dean we know is already gone?"

"You can't think like that. Dean is strong. No matter how much the Mark is influencing him right now. Believe in your brother, Sam. He came back from hell, from Purgatory…stopped the apocalypse… he has been through so much and he always came out on top."

Sam sniffled and nodded. Cas was right. With renewed determination he picked up the papers from the floor and returned to his research.

A couple of hours later, Sam was brought out of his reading by the insistent ringing of his phone. A quick glance at it showed him it was an 'unknown number' calling. He was half tempted to ignore it, a new hunt was the last thing he needed right now, but when it wouldn't stop he dropped his pen with a sigh and grabbed the phone.

"Hello?" His frustration was clear in his tone.

"Sam? Hey it's Garth."

"Garth? Uhm, hi! It's good to hear from you again. How are you doing?"

"Yeah, good to hear from you too, Sam. But this is not a social call, I need your help."

That was just what Sam had expected. He tried to get rid of Garth in a somewhat friendly way. "Listen, if this is about a hunt, I'm kinda busy right now…" But the other man interrupted him before he could continue.

"It's not a normal hunt, to be honest, I have no idea if we even should do anything at all, but it's killing people as well so – I thought I run it by you and Dean. You guys are the best hunters out there and if you say it's nothing, then I'm inclined to agree."

Sam's barely existing patience was wearing dangerously thin. "Garth, out with it."

" , right. Someone is killing demons. And not just a few here and there. The body count is in the dozens, and it is rising quickly."

Sam felt the hairs at his neck raise up. "How are they killed? And how do you know that it is demons?"

"They're stabbed, beheaded, cut apart; some are pretty much shredded to pieces. It's gruesome. And we know its demons because the last raid was not far from here. I checked the bodies. There were traces of sulfur in their throats, which is a safe sign for possession. That, coupled with the rumors that there has been a change in power down-under – and I know you guys were involved in that by the way – it looks as if the new king is getting rid of Abaddon's loyalists. And he does not care much about the innocent humans that they have taken as vessels."

Halfway through Garth's tale Sam had closed his eyes in despair. Now he fought to find his voice.

"Garth, did you- does anyone else from the hunting community know what you just told me?"

"What? No, like I said, I wanted to hear your opinion first before sending out an alert."

Sam scrubbed his free hand over his face in relief. "Good, that's good. Now listen to me, what I'm about to tell you is meant for you only, ok? Can I trust you to keep this secret?"

"Man, come on, you know me! You know what I am, and you still doubt me?"

"Yeah, no, of course not Garth. It's just, I've been on edge for a few days and…" He sighted. "I'm sorry. I know that we can always trust you." He took a deep breath before he continued. "I know who is killing those demons. And it's important that you keep hunters away from him for two reasons: First, it's a Knight of Hell and they are almost impossible to stop, trust me on this, we have tried! And second, the Knight… it's Dean."

"WHAT!? Dean is possessed by a Knight of Hell?"

"No Garth, worse. Dean _is_ a Knight of Hell. He got tricked by Crowley and took on the Mark of Cain which would allow him to kill Abaddon with the First Blade. Unfortunately we did not know that killing the last Knight would automatically transform him into the next one. He- he turned into a demon right in front of my eyes… and…" His throat closed up and he found he couldn't continue. He was glad that Garth couldn't see him through the phone.

"God Sam, I am so sorry! I had no idea. How -" He quickly abandoned the question. It was clear how Sam was doing- and it wasn't fine. So he rephrased. "What are you doing about this?"

"Castiel and I are trying to locate Cain, he is the only one who has ever resigned from that position, and we hope that he can tell us how he did that. But it is tough goin'. Listen, can you send me everything you have on those killings? It might help us track Dean."

"Sure. Let me hit my sources, I'll see what I can dig up. And don't worry about the demon killings, I'll keep a tab on it, and if anyone is stumbling upon it I'll make sure they back off."

"Thank you Garth. I appreciate it."

"Don't mention it. I hope you find a way to help Dean, I really do. Let me know if there is anything I can do to help. Anything, ya hear me?"

"Yeah. I will Garth. Take care, ok?"

"You too Sam."

And with that they hung up. Sam slowly lowered the phone to the table, deep in thoughts. When he looked up again, Cas was standing next to him, two mugs of coffee in his hands. Sam smiled gratefully and took the cup from the angel, motioning him to take a seat next to him. They needed to talk.

xxx

Dean stood over his latest victim. The act of killing alone didn't satisfy him any longer, he needed to inflict pain. So this one had suffered all of his anger before he finally killed it by cutting the head off. He looked closer at the mangled dead body on the floor, and for a brief second a flash of a different brown haired man, lying bleeding and lifeless on the floor took the place of this one. He shook his head and the image vanished. Dean wondered who that was, the strikingly blue eyes seemed so familiar, but he couldn't quite place them. The blade vibrated slightly in his palm, and he forgot about the blue eyes immediately. Focusing back on the task at hand, he pulled out a bowl to collect the blood of his victim, preparing to call Crowley with his latest update, eager to get to his next assignment.

* * *

_Yeah, I like angst... and reviews! Please? _


	3. Chapter 3

**AN:** I'm sooo sorry for the long wait! I needed some time to figure out where this story is going and this chapter kinda sets up the rest of this tale. And can I just say how much pain in the a** continuity and logic are? I think I rewrote the thing at least 3 times. Still not 100% happy with it but if I wait for that then you would never get to read it… Let me know what you think!

All your kind reviews, follows and favorites helped me so much, because I knew that I have readers out there that want to know how this story ends! There is no better motivation for a writer, so thank you!

**Warnings:** Urm, the usual, dark themes, violence, implied violence against a child (sorry!), blood

* * *

Castiel sat on the hood of the Impala. They were taking a well deserved break from the research and he had wandered around the bunker restlessly, until he came across the garage, and its prominent occupant. Seeing the car standing alone in the dark had moved Cas more than he would ever admit, but the Impala was so irrevocably connected to his best friend that its lonely form pulled him in.

Thinking back to the day when he had found out about the mark, Cas got lost in his own memories.

**Several weeks ago:**

_Back in the bunker, Dean pulled off his jacket and threw it carelessly over a chair while rolling up the sleeves of his shirt. Cas, walking besides him, suddenly inhaled sharply and grabbed for Dean's right arm. _

_Dean quickly wrenched his arm out of Castiel's tight grip, startling the angel. "It's nothing, Cas. Don't worry." He said dismissively._

_But Cas ignored him. With a speed that yet again reminded Dean that he was indeed a very powerful being, Cas gently but firmly took Dean's arm again and slowly pushed the sleeve further up, revealing the complete mark burned into his skin. The angel's hand trembled as it hovered over the mark, careful not to touch the red skin. _

_"Oh no." whispered Cas, unable to hide the worry and shock on his handsome features. His gaze hardened as he looked up and his blue eyes turned to steel. "Dean, how did you get this?" _

_He flinched under the harsh words, but quickly composed himself and replied. "Cain gave it to me. Apparently it is necessary in order to wield the first blade, the only weapon that can kill Abbadon." He defended himself. _

_Castiel released Dean's arm and turned around, leaning heavily onto one of the library tables. He needed to regain his composure; otherwise this would turn ugly really quick. Once the angel turned back around his eyes shone bright with barely concealed fury._

_"How could you do this? Do you have any idea what this mark stands for? What it will do to you? What damage it has already caused?" He hissed, anger accenting every single syllable. Dean looked like a deer caught in the headlights. _

_"Um, no?"_

_"Dean, this is the mark of a murderer. THE murderer. The first one, and it was given to him by Lucifer. That in itself should have given you a clue, but let me ask you this: Do you feel more restless? More ruthless? Have you killed anything lately that you could have just as easily let live?"_

_Dean suddenly found the pattern on the floor extremely intriguing. _

_"Yes." His voice was barely above a whisper. "Yes, ok? Hunting makes me – I don't know, it makes me feel good. I can forget all the crap that's in my life and just focus on the job. And if I get a chance to smite the bad guy, hell yeah I'm gonna take it! Does that make me a bad person? Ya, probably, but Cas, that has always been in me. That isn't just the mark…."_

_"No, but the mark is enhancing it. Lets you forget reason. Lets you ignore the pain. Makes you stronger, physically and mentally." _

_"So what? It helps me to be a better hunter. Can't see anything wrong with that! And I will be able to gank that bitch Abaddon. Cas, I am fine. And hungry. Gotta run to the store, can I get you anything?" And without even waiting for Cas' reply, he left. _

Back to reality, Cas realized just how badly he had handled that confrontation. And as a result, Dean had retreated even further from him. Instead of helping his struggling friend, Cas had driven him away. Before he could get more into his musing, the door opened and Sam stormed in, clearly excited.

"Garth found a trace; he thinks he knows who Dean will go after next. If he is right, this could be our best shot so far to finding him. But we need to leave right now!"

Gliding off the hood, Cas walked over to Sam. Maybe he still could save his friend, maybe there was a way to make all of this right. With a hopeful smile he asked "So, where are we going?"

xxx

Dean stood in the shadows of a large tree, watching over a quiet residential street. In front of him was a perfectly ordinary suburban neighborhood, complete with manicured lawns and children's toys spread out in front of double garages. There were supposed to be four of Abaddon's followers hiding in the well kept home at the end of the road. His next targets. He used the cover of the backyards to get closer. Stealthily he picked the lock at the back door and entered the dark and silent house.

The demons had not seen him coming until it was too late. He surprised two of them in the living room, and attacked with long honed skill. In one fluid motion he sidestepped the first demon and continued his move by stabbing him in the back. Without losing a step he twisted the blade out of the body and whirled around to cut off the head of the second demon. He took a breath and looked in appreciation at his handiwork. He preferred to take more time in killing his prey, but then, there were still two demons here. Right on cue, a young female stepped into the room and immediately took in the situation. Reacting with lightning speed, she tried to flee the body, but Dean was in front of her and had the blade to her throat before more than a few tendrils of smoke made it out of her mouth.

"I really wouldn't." He said in an icy tone.

"Please. Please don't kill me. Send me back, I'll serve him…"

"Sorry sweetie, Crowley doesn't do second chances." With a flick of his wrist the blade cut through her throat. Not deep enough to kill her immediately, no, she would bleed out slowly and Dean was going to watch.

A sound from the hallway caught his attention. He readied his weapon and crept around the corner. Dean froze. In front of him stood a little girl, no more than six years old, watching him with wide eyes. His mind told him that this was just another demon, another easy kill, and the blade buzzed eagerly in his hand, but something held him back. Something deep inside him had woken up and reminded him that this was just an innocent child. He shook his head to clear the confusing thoughts and refocused at the task at hand. Approaching the trembling girl, the feeling of wrongness intensified. And suddenly he found that he needed to protect the child.

"Leave this body." He commanded coldly.

The trembling stopped and a hostile smile appeared on the previously terrified face. "No. She is mine." The demon was speaking with the girl's voice, but the tone of defiance was not childlike at all.

Losing his patience, Dean pressed the blade to the girl's throat. "Last chance, leave this body and live or stay and die."

Turning her head, she glanced at the other bodies in the living room, and raised her eyes back up to Dean. The demon didn't need any further incentive; he fled in a cloud of black smoke. Dean knelt down next to the girl and held her as she gained consciousness again.

"It's over, get out of here." She just stared at him with big eyes, frozen in terror. "Run!" That got the girls attention and she scrambled to her feet and stumbled out of the door. Dean watched her leave.

"Well, well, I see you have been busy here."

He whirled around in surprise. "Crowley. What do you want?" He snarled.

"Just making sure that my orders are followed."

"You already know that they are. Look around you!" He motioned to the three bodies on the floor.

"But are they? I just saw a little girl running out, and I can't help but notice that the body count is one short."

Dean bit his lip, but remained quiet.

"When I say kill 'em all, then I expect that you Kill. Them. All. No matter what pathetic meatsuit they hide in. This," he motioned to the entrance door where two of his servants held up the little girl, "is not tolerated! Now, kill her."

"The demon is gone. He fled. This is just an innocent girl!" Dean argued.

"Well, thanks to my general paranoia, I had a few of my guys watch you. They caught the demon and forced him back into his body." As proof, the eyes of the girl flashed in black.

"No." Dean walked towards Crowley, challenging the demon. But Crowley stood his ground. When he spoke, his voice was calm, but menacing at the same time.

"Don't forget who the true master of the blade is. I gave it to you – I can take it from you. Do you really want to test my tolerance?"

Lips curled into a snarl, Dean lowered his head in defeat. The blade vibrated slightly in his hand, as if to remind him where his loyalty belonged. He felt his anger subside slightly. Crowley controlled him, but the young knight was not one to give up easily. The time would come when he could rebel against his master, but it was not now. For now, he had to surrender to the king's orders. He turned towards the girl and readied his weapon.

xxx

The body was still warm. He had missed his brother by mere minutes. Sam slammed his fist into the concrete pillar. The searing pain in his hand temporarily distracted him from the latest failure. So close, he had been so close this time. This was the third location in the past week that Dean had hit, and every time he had been a little bit closer on his brother's trail. Garth had not exaggerated about the gruesome nature of the murders. The bodies he had found so far had been in a horrifying state. The amount of blood had been hard to stomach, even for him as a seasoned hunter. The thought that his brother was doing this was almost unimaginable and Sam felt sick when he imagined what Dean had become.

He fished his phone out of his pocket to call Cas, maybe the angel could discover something here that could help them. Suddenly he saw some movement out of the corner of his eye. His hand flew to the gun that was tucked in his waistband, and he hissed as his injured knuckles complained about the sudden motion. Sam crouched down slightly and very carefully made his way across the warehouse.

Dean couldn't believe it. Out there, bent over his latest victim was the last person he needed on his tail right now. At the same time, simply seeing his baby brother again brought up a familiar ache. A longing that ran so deep within him that the mark could not erase it. He shuffled his feet, trying to get a better look at Sam when he realized his mistake. He'd been made! His first instinct told him to teleport out of there, but something held him back. True, he wasn't done with the body yet, but that wasn't it. It was Sam. He couldn't tear his eyes away from his brother. He crept further into the shadows and hoped that he wouldn't be spotted.

"Dean? Is that you?" Going against his training, Sam put the gun way. "If this is you, I just wanna talk, ok? Please…"

"There is nothing to talk, Sam. You need to get out of here."

"Dean! Thank god."

"Sam, get lost!"

"No." Sam stepped forward a few steps and stood tall in the large room. "I just found you. You want me gone? Make me!"

The challenge was more than Dean could ignore, and he stepped out into the light. Sam gasped at the sight of him, but he did not move.

"What do you want?"

"I just wanna talk. You – this- The blade, it's like a drug for you, isn't it? I know the feeling. Don't you remember? I just to be a junkie, and it turned me into something that was not all that different from you now. You refused to give up on me then. And now it's my turn to return the favor. You can fight this. WE can fight this."

"No." he growled. "You seem to be under the impression that I want to give this up. That this is wrong. But I feel great! Why would I leave this?" He used his powers to push Sam against the nearest column. "This power… it makes me the most lethal being out there. This is what I was always meant to be."

"I refuse to believe that. You are killing the demons, but what about the vessels? That little girl…they were innocent human beings."

"Never stopped us before." He stared coldly at Sam. There was no trace of humanity anywhere in his features. "Don't be such a hypocrite, Sam. You have killed your fair share of vessels, both angels and demons, without batting an eye. The mark makes me stronger, faster. It makes me the perfect hunter."

Sam sadly shook his head. He had to remind himself that this was not really his brother speaking. This was a twisted, cruel version of the man he had looked up to all his life. Anger rose up in him as he looked into the black orbs that had replaced kind green eyes. Giving up on pleading, he let his rage take over. "A hunter? Like this? No Dean, you're not a hunter any more. You're a demon, a –"

"Sam, don't!" Cas' voice came clear through the large space, stopping Sam from saying something he might regret later on. Dean froze. His brother he could handle, but he wasn't so sure how he would fare against the angel. So he took the easy way out. He vanished. Sam slumped down the pillar and looked up at Cas, shock and remorse all over his face. He had almost called his brother a monster, and he suddenly remembered how much those same words out of Dean's mouth had hurt him.

"Rage is not the solution, Sam. It will only drive him away further. If you want to gain his trust again, then be understanding. Be supportive."

xxx

It had been a week since his brother had disappeared again and after days of dead-ends Sam sat in the empty kitchen, staring at a half empty bottle of whiskey. Cas had returned to heaven for a while to try and dig up more info about Cain, while Sam had been through Garth's latest reports and research countless times. Without any success. He was at breaking point and he dealt with it in true Winchester fashion: Booze.

Not having the alcohol tolerance of his brother, the half bottle was enough to have Sam utterly wasted. But it numbed the pain, helped him forget the misery that his life had turned into, and he was not ready to give up on that feeling. He grabbed the bottle to take another swig, but his coordination was shot and instead of grabbing the whiskey, he propelled the bottle off the table. The loud crack startled Sam. He watched the bottle shatter into a thousand pieces and felt this was strangely symbolic of his life now.

Sliding to the ground, he wrapped his long arms around him and tried to hold himself together. That's how Castiel found him a few hours later. Still heavily drunk, but able to form words again, Sam greeted the angel.

"Cass… good t' see ya…." He slurred, squinting his eyes in a fruitless attempt to clear his blurry vision.

Castiel simply looked at him with distaste written all over his face. Sam didn't care, he was drunk, and happy to have someone to talk to!

"My broth'r is a deeemon. An' y-you are a – an aangel… I'm seein' aangels…." He smiled happily and Cas lost whatever patience he had and put his hand onto Sam's forehead. The hunter, confused, blinked and then flinched away from the touch.

"Cas! The hell…?" Suddenly shockingly sober, he scrambled back on his feet.

"Sorry to crash your party, but I don't have time to wait until you are done with your self-pity. I found something, and you better have a look at it. Sober." He put an ancient looking scroll onto the table and nudged it towards Sam.

The hunter took it and unrolled it carefully on the table. The content was hard to read and in a language that Sam had never seen before. He looked questioningly at Castiel.

"That's a locator spell for Knights of Hell. Current _and_ former!" He paused to let the news sink in. "And I have all the ingredients with me."

"Then what are we waiting for? Let's go and find Cain!"


	4. Chapter 4

**AN:** Ok, ok, so 'King of the Damned' ruined my little theory here and shoved this little fic firmly into AU territory. But I still think that Demon!Dean is a strong possibility, especially after this week's 'Stairway to Heaven', which was just mindblowingly awesome!

Again, sorry this took so long to upload, my muse and real life were just not cooperating. But the rest of the story is all typed out, and only needs some edits. I plan on having it all up before the season finale! (And yes, I know that's less than a week away!)

**Warnings: **dark themes, but nothing explicit.

* * *

Sam watched anxiously as Cas added the last ingredients into the bowl and began reciting the enochian incantation. The spell was fairly complex, and it had taken them the better part of two hours to get through all the steps. Now they were finally done and Cas poured the bright red fluid over a large map. The paper absorbed the liquid, and then black spots started to appear all over the map. They grew in size and merged into each other, until there was only one tiny spot left untouched. Sam leant in closer to decipher the name of the town, but as he realized the location and then the name he dropped his head low. Great, of all places Cain could hide…

"We need to repeat the spell, Cas."

The angel looked up and furrowed his eyebrows. "Why, what is wrong? Did it not work?"

The confused look on his friends face made Sam smile. No matter how long he knew the angel, the childlike innocence he sometimes portrayed never ceased to amaze Sam. "Oh, it worked fine," he chuckled, before turning serious again, "but the location it identified is too big, we need to repeat it on a smaller scale map. More precisely, on a city map of New York. Without an exact address we'll never find Cain amongst eight million people!"

Understanding, Castiel nodded and silently prepared to repeat the spell, while Sam searched the archives for a suitable map of New York City. Once he found a somewhat recent three by five feet wall map, he returned to the library. They worked in compassionate, although slightly tense silence as they prepared everything. The repetition of the spell worked and this time the result was clear, down to a block. And really, Sam thought to himself, he should have been able to guess this! Cain was living in Hell's Kitchen. Oh sweet irony!

xxx

Crowley sat down behind his massive desk and pondered his decision. It was a risk sending his knight on this particular assignment, but he had no one else in his ranks he could trust with this mission. No, this was the right call. Dean was ready.

Crowley's gaze was guarded as he watched his knight enter. There had been no further disobedience after the incident with the girl. And he had made sure to test Deans loyalty thoroughly. The knight never faltered in his ways, and the trail of blood and grime he left in his wake was impressive. Crowley knew that even after the 'incident' as he liked to call it, there had been resistance in Dean, but with carefully plotted incentives and motivations, this resistance as well as all remaining traces of humanity had left the knight a while ago. Now he was ready to be unleashed onto the world.

"Here is your next assignment." He handed over a small slip of parchment, with two names written on it. Dean read the names, and then raised his eyes up to his king. "I trust you will have no problems?

"No," came the gruff and singular response. "Consider it done."

"Good. Then you won't mind me taggin' along."

"I got this."

"You will forgive my slightly broken confidence in your loyalty after the last _incident. _And-" he paused melodramatically, "I would really like to see this. From a purely professional point of view, of course. I need to go topside once in a while, hell can become a bit of a bore."

"Fine." And that was all answer Dean was willing to give before he teleported away. With a sigh, Crowley followed.

xxx

Cas had teleported them to a quiet alley about a block away from Cain's address. They carefully walked towards the demon's house and Sam let out a sigh of relief when he saw that the building had only three stories. That made the search much easier.

Cas held out his hand to stop the young hunter from walking any further. "Let me go in first, I will be able to identify the correct apartment without drawing any attention."

Sam nodded. Angel recon definitely beat any kind of research he was able to do! He leaned against the building across the street and tried his best to blend in with the city crowd. Having been on the road pretty much all his life, big cities were fairly unknown territory for him and he suddenly missed the open space of the mid west. Before he could get lost any further in his own thoughts, Cas was back at his side.

"We are in the right place. Top floor, apartment number 23."

Two minutes later, and they were standing in front of a shabby looking door on the second floor. Sam knocked. Nothing happened. Trying again, Sam pounded his fist against the door and called "Cain, we know you are inside. We need to talk to you!"

"No. You need to leave! Angels are not welcome here." Came the gruff response through the closed door. Sam glanced at Cas, who just shrugged. Unwilling to give up, Sam tried again.

"Please! This is about Dean." He was met with silence. Then the lock clicked and the door opened marginally. Sam took this as an invitation to continue. "My name is Sam Winchester and this is Castiel. We mean you no harm. Dean is my older brother, and I think you have a good idea why we are here." After a few seconds of apprehensive waiting, they heard the chain being removed and the door opened.

"So he has found the blade then?" Seeing Sam nod, Cain pressed his lips together and shook his head slowly. "I tried to warn him, but he wouldn't listen. Stubborn idiot, your brother. Reminded me of myself when I was younger." Then he motioned them to step inside.

The apartment was clean and sparsely furnished. It had nothing of the homeliness of Cain's old house and even though Sam had never seen that place, he knew with one look that this current location was only a temporary hiding spot. Apart from a framed picture on the side board, the apartment was void of any personal items. Cain motioned them to take a seat at the couch, while he remained standing, eying them cautiously.

"You are here to find out how to kill him, I presume?"

"Kill him?" Sam's eyebrows shot up to his hairline in surprise. "No, god no, we want to find a way to save him. See, you managed to leave; you put away the blade and lived a quiet life. I want to know what made you do it, so that I can help my brother take the same path. I just want him back."

The older man remained passive, but his eyes had softened during Sam's speech. "What has happened to Dean is not reversible, Sam. I'm not bearing the mark any longer, but I'm still a demon." Just as proof he turned his eyes black. "You can't save your brother. If he wants to abandon the blade and the ways of a knight, then it has to come from inside. There is no magic cure."

Sam winced. He hadn't expected to find an easy way out, but to be told so bluntly that there was no chance at all, the sheer thought devastated him. Seeing the stricken face of the younger Winchester, Cas spoke up. "What if there was a way to cure a demon?"

That caught Cain's attention. "Are you referring to the cleansing ritual? Injecting human blood into a demon's vessel?"

"Yes! That will work, right?" Sam asked, a spark of hope growing inside his chest.

"No Sam, it won't. Not on Dean, not on me. It works on demons that are possessing humans, forces them to access their vessel's emotions, even if the vessel is already dead. But Dean has never taken a vessel and neither have I. We are First Born, humans that were turned into Demons while they are still alive. The oldest and most powerful rank amongst all of hell's armies. That's why I was charged with training the Knights of Hell. And that's why Crowley was so keen on creating his own lapdog, he knew I would never submit to his rule, but he still needed a knight to fortify his position as king."

Sam stood up and began pacing halfway through Cain's tale. Hands working along his thighs, clenching and unclenching in a nervous, subconscious way. As he realized that Cain had stopped, he whirled around and asked: "Wait, but I thought Dean was a Knight of Hell? Now you are saying he is not?"

"He is _the_ knight. The knight of knights, First Born, and second in power only to the King of Hell himself."

Sam stared at Cain in utter shock. Cas had gotten up as well and put a comforting hand on the hunter's shoulder. This had just gotten so much more complicated. They had barely managed to kill Abaddon, and only done so at great cost, and now it turned out that Dean was even more powerful!

"You- you knew?" Sam stuttered, enraged. "When you passed the mark to my brother, you knew this would happen?"

Cain met his intense stare. "No. But I knew it was a possibility. Had he asked, I would have told him. But he never did."

Before things got more heated, Cas brought the conversation back to the reason of their visit. "That certainly makes things more complicated, but it does not change why we came to you. And now you are even more important, as you are the only one in existence that has borne the mark and managed to escape its influence. You overcame its power, you stopped behaving like a demon. What made you leave behind that life?"

With a sigh, Cain let go of the tension, sat down in an armchair and folded his hands under his chin. Sam remained standing, still too agitated to sit still.

"Like Dean, I had no idea what I got myself into when I took on the mark. The exhilaration and power, it makes you forget every reason you ever knew. It makes you forget that you are human and turns you into something much more feral. You don't question why you kill, you don't care about the lives you end. And then, after centuries of murder and rage, I met Colette. The sweetest thing I have ever laid my eyes on. God, I loved her so much. She wanted me to stop the murder, and so I did. Killing all the remaining Knights of Hell was my farewell. I was ready to put the blade down. But Abaddon betrayed me and killed Colette right in front of my eyes." He paused, taking a moment to collect his thoughts.

"My last promise to her was to stop. So I stopped. It was the hardest thing I ever did, but I stopped. For her. I have lived a quiet life in hiding ever since. Until the day your brother and Crowley found me. I broke my promise that night, and for that I will ask Dean to kill me. There is nothing left for me here."

"Love… that makes sense. It would take a powerful emotion to counter the influence of the mark." The angel had no problems connecting the dots. Cain nodded in agreement.

"Yes," he began, looking sad and slightly disheartened, "but you are forgetting that I had _millennia_ to learn the powers of the blade, to grow tired of the life as a knight. Dean has just started his journey, you expect him to have the strength to shed this exhilarating feeling within weeks of getting it?" Cain shook his head. "As much as I want you to succeed, I really don't think you have even the slightest chance." He paused and looked into both of their faces. In resignation, he added. "But I see that you will still try. If you want your brother back, you need to remind him of his humanity. And why he took on the mark in the first place. Give him a reason to want to return."

Sam was determined. Simply because someone told him it wouldn't work didn't mean that he wouldn't give it his best shot. But his connection with Dean was feeble at best and Dean wasn't exactly known for forming loving, or for that matter, lasting relationships with his female acquaintances. Still mulling over Cain's words, something jumped out at him. "He took the mark to kill Abaddon! How is that-"

But Castiel interrupted him. "No Sam. Killing Abaddon was his target, his motivation was something else. He took the mark to avenge his grandfather. To protect his family. Protect you! You need to trust in your brother's strength."

The moment he heard the words come out of Cas' mouth, Sam knew they were true. He might not want to hear them, he might not want Dean to protect him, but he knew that this was the main driving force that kept his brother going. Family. And now, with things so messed up between them, Sam was certain he was the last person that could get a positive reaction out of Dean.

Not ready to share this with the others, he changed the subject: "There is one thing I don't understand. You are still around, and you are still a demon. How come Dean was turned into a knight? From what we understand, that only happens to whoever kills the last knight?"

"When I resigned from the job, when I abandoned the blade, I lost the title. Still a demon, but no longer a knight. Abaddon was the last one. Now Dean is. If he gives up the blade out of his own free will, then there will be no more knights."

Cain's theory seemed sound. Sam was relieved to know that there was a way to get his brother back, even though he had not the faintest clue how to pull this off. He looked at Cas, asking the angel silently for help.

"No Sam, this is something only you can do. Dean values family above everything else, and that leaves only you. For once, be completely honest with yourself, and with him, and you will find that there is a way. I will assist you, but I can't do it for you. If you don't find the strength, then Dean is truly lost to us."

Watching the younger Winchester with keen eyes, Cain spoke up. "Your brother owes me. I can call him here, but you better be ready!"

Sam's eyes grew wide in panic. He wasn't ready, he was nowhere near ready for this! He was about to tell Cain to wait when he heard the door open.

"Kind offer Cain, but that won't be necessary. I'm already here."

* * *

_Dun dun dun…. So, any ideas who Dean is supposed to kill? 4 in the room, only 2 names on his list… _


	5. Chapter 5

**AN:** As promised, here is the final chapter! And in time before the grand season finale tomorrow. This was quite an emotional chapter to write, and it marks the first time ever that I changed the plot radically because I simply could not write a certain scene. Simply couldn't - as in my fingers were reluctant to type the words that were in my mind. And while I'm still a bit sad to loose that particular plot line, I like this version so much better.

**Warnings: **dark themes, blood, violence, character death, and maybe the faintest hint at Destiel

* * *

_"Kind offer Cain, but that won't be necessary. I'm already here." _

Sam's head whipped around as he heard the familiar voice and sure enough, there was his brother standing in the doorway. But it wasn't really his brother. The last time they had faced off, Sam had still seen traces of Dean behind the demon eyes, now, they were gone. And Dean was not alone. Crowley had entered behind him, a gloomy grin on his face as he spoke.

"Are we crashing a party here? Sorry to interrupt!" He looked at his knight and said in a commanding voice. "You have your orders. Execute them."

Dean's eyes flickered to Cas, he knew the angel had the power to stop him, and Crowley saw the hesitation in his knight. He really did not want to leave the scene, but he knew that Castiel would complicate matters. "Ah, don't worry, Castiel and I need to have a long overdue chat about alliances and betrayal." And with that both Crowley and Cas disappeared from the room.

Cain was the first to recover from the shock and addressed Dean. "I warned you of the dangers, Dean. For what it's worth, I'm sorry for putting this on you. But we both know it was your choice that brought you here."

A feral growl was all the response Dean gave as he stepped closer towards Cain.

"I assume you are here to kill me? Well then, go ahead." He spread out his arms in surrender and Dean didn't hesitate. With one swift move the blade sailed through the air and connected with Cain's throat, cutting seemingly effortless through skin and bone. The former knight was dead before he could feel any pain.

Sam gasped in horror. The precision and coldness of the kill chilled him to the bone. He had seen his brother kill countless creatures, but there had always been either imminent danger or just cause. This was neither, it was coldblooded murder, and the complete lack of empathy on Dean's face sent shivers down his spine. Before he could recover, Dean turned around and faced him. Sam blanched.

"No. No, Dean, it's me. It's Sam." Next thing he knew, he was flying through the room until his back connected painfully with the wall. The impact paralyzed his diaphragm and he gasped for air, desperately trying to force his breathing back under his control while he scrambled to get back on his feet. Dean approached with swift steps and Sam prepared for the imminent attack.

He tried to move into a defensive position, but the speed with which Dean approached left him no time for preparations. In the end, it was the years of sparring that saved Sam's life. He recognized his brother's intention and in a split second before the attack, he kicked out hard against Dean's leg, throwing him off balance. It wasn't enough to thwart the attack completely, but instead of the intended stab to the heart, Sam felt the blade enter his lower abdomen.

He screamed in agony as crippling pain shot through his torso. Unable to move, unable to breath, he tried to regain focus in his blurry vision. His consciousness was slipping but he held on with all his strength, reaching out to Dean in a last desperate attempt to break through to his brother. He knew that he couldn't block another blow; he felt his strength leave him with alarming speed. This was his last chance, or he would die at his own brother's hand.

"Dean, please….." he wheezed through clenched teeth.

He didn't know if he imagined it, his vision was slowly turning fuzzy, but it looked like the black eyes flickered briefly back to green for a second. Sam summoned his last remaining energy and whispered:

"Brother, help me."

xxx

Dean froze, black eyes shining intensely, looked onto the body in front of him. He was ready to finish this assignment, but something held him back. He could hear words, but they didn't register, not until he made out one word, the one sound that held insurmountable power over him. "Brother." No more than a whisper, but in the voice of Sam, this was his brother calling for him, begging him for help and that woke the strongest instinct that Dean had ever known. Protect Sam. Take care of your little brother. Never give up on family.

Dean struggled, as two sets of thoughts raced through his mind, fighting for control. He started to tremble, the blade commanding him to finish his job, but then he shifted his focus and pitch black met pleading green eyes. Curious, he thought, Sam's hazel eyes seemed to change color based on his emotional state, they could look as blue as the sky, brown as timber or any shade in between. Right now they were green, mirroring Dean's own eye color. The look on Sam's face was expressive, it showed concern, pain, hope but most of all, it showed love.

The eyes of his brother were staring into him, blazing through walls of defenses like they were made of cardboard and reached into his very core. Dean felt something inside of him break and familiar warmth was spreading through his chest. He stared at his brother with wide eyes, trying to untangle the conflicting emotions inside of him. He didn't want to let go of the power, but this was Sam, and he needed him. He couldn't, wouldn't disappoint his little brother.

Dean dropped the blade from his hand as if it was hot. He staggered back and his mouth opened, but no words came out. He looked down at his bloody hands and then up at Sam, as if trying to connect the two. Then he stammered with horror:

"S- Sammy? Sam…?" His gaze fell on the bloody mess of Sam's stomach and suddenly his entire world tilted on its hinges. Grasping his head in a desperate attempt to keep it from exploding he collapsed to his knees, chanting maniacally "No, god, no, no…." He crumbled to the floor, whole body wracked by shivers and curled up into a tight ball.

xxx

Sam slowly slid down the wall, both hands pressed around the blade trying, and failing, to minimize the blood flowing out of the deep wound. He knew that if Dean had pulled the knife out he would have bled to death within minutes. But with the blade inside of him he might make it for a little bit longer. He looked over to his brother, who was curled up on the floor. What really frightened him were the sounds he made. It didn't even sound human, more like the screeching of a wounded animal. He wanted nothing more than to crawl over to him, gather him in his arms and help him through this, but moving was currently out of the question.

And that was when it hit him just how severe the situation really was. If he couldn't get them help, then there was a very real possibility that they would both die. He mobilized his remaining strength and shifted his weight, trying to reach the mobile phone he felt in his back pocket. Clenching his teeth against the pain, he managed to pull it out. It felt wrong in his hands and as he brought it up in front of his face he realized why. The screen was shattered and the phone was dead. He would not be able to call for help. Letting his head fall against the wall he sent out a desperate prayer to Cas.

xxx

Cas appeared back at the apartment shortly after he heard Sam's urgent call for help. Looking more than a little disheveled from his confrontation with Crowley, he grasped the back of a chair for support. He wasn't sure whether his knees were weak because he just fought the King of Hell or because of what he was facing now.

"Oh no," he mumbled as he took in the scene in front of him. Cain was obviously dead, but he hoped that it was not too late for the Winchesters. Stepping over to Sam, who looked more severely injured, he surveyed the younger man's injuries, but the source of the blood that was pooling around him was not hard to find. The First Blade was still firmly lodged into his stomach. He stretched out to feel for a heartbeat, terrified that he might not find one, and sighed in relief when his searching fingers found a weak, but regular throbbing. With urgent efficiency, Castiel pushed Sam's hands aside and grabbed the hilt of the ancient knife, pulling it out and immediately covered the wound with both hands. Eyes closed in concentration; he called up on his grace to heal the bloody mess that was his friend.

xxx

Sam awoke with a gasp. Arms trashing around, narrowly missing Cas, it took him a moment to orientate himself and to remember where he was. His hands flew to his stomach, astonished to see the wound completely healed. He met Castiel's worried eyes and gave the angel a grateful nod.

"Thank you."

Cas simply smiled tersely, then turned around to look at the other Winchester. Sam followed his glance and saw that his brother was in the same spot as before, but now he was deadly still.

"No, Dean. DEAN!" he shouted and crawled over to his sibling, feverishly searching for a pulse. "Don't do this to me, please….oh thank god," he breathed as his search was rewarded. He turned around to Cas, about to announce the good news, when he noticed the angel hadn't moved from his previous position. He looked closer and saw that the usually spotless trench coat was torn up and bloody.

"Crowley." Sam snarled.

"He won't interfere for a while." Sam raised his eyebrows in silent question. "Banishing spell. Crude, but effective." Cas explained curtly, obviously not willing to offer any further details. The angel slowly stood up, but Sam noticed that the he was unsteady on his legs, using the wall for much needed support

"Hey, are you all right?"

Cas smiled sadly. "No. My grace, it's weakening. But that is not important right now. What transpired here? How is Dean?"

Sam quickly recapped the events that had left them in their current predicament. While talking, he carefully cradled Dean's head in his lap, savoring the long denied contact. As much as he had needed and wanted the distance from Dean, their strained relationship had hurt him just as much as he knew it had hurt his brother.

Cas listened with a deepening frown. "This is not unexpected. Cain said that love was the only thing that can reach a knight. It seems that his love for you conquered the influence of the blade, at least temporarily. He is currently locked in his own mind; the conflicting emotions have forced him into this meltdown. We must act quickly to ensure that he will win the fight against the influence of the blade."

"How?"

"There is a way to reach him in this state, but it will not be pleasant for either of you. Or me. I can connect your minds, break through his defenses and show him your thoughts and emotions. It's dangerous, but it might be the only way to get through to him."

"Do it." Sam was determined to try anything to get his brother back.

But Cas cautioned: "Sam you have to be aware that I can only direct your thoughts to him, I won't be able to see or filter them. So whatever is going on in your mind, he will be able to see it. No secrets."

That left Sam reeling. There was a lot of private stuff on his mind, things that Dean could – and should - never know. "Will he remember any of it?" he asked, slightly uneasy.

"That's hard to say, but I would think some of the memories will remain, yes."

Sam nodded. Full disclosure was not something he was very comfortable with. But this might be his last chance to get Dean back, so he would take it. And all the lies and secrets had only driven them further apart in the past. Maybe it was time to finally share the truth. They could deal with the outfall afterwards.

"I understand. I'm ready."

Flashing one of his rare smiles, Cas put one hand on Sam's forehead, then quickly pushed his other hand against Dean's head. The connection was established instantaneously and the three men froze, eyes closed, but pupils moving rapidly.

Castiel crushed through the walls surrounding Dean's mind with practiced ease. What he saw once inside almost made him break the connection. Dean's usually bright and glowing soul was tainted; whirls of black had taken over large parts. Acting on impulse and without thinking, he opened a link to his own mind as well as Sam's. Maintaining this three way connection would take a lot of his strength, but Dean needed to see how outsiders saw him, how much he really was worth. He needed to see a reason to win this fight raging on in his mind.

xxx

Cas broke the connection when he felt Dean retreat from the mental link and took a step back to give the brothers some privacy. He had only seen flashes of Sam's own thoughts, but some of those were deeply personal, and he was sure they were not meant for his eyes. Unfortunately, this invasion of privacy was the price they all had to pay for the chance to save Dean.

Sam still cradled his brother in his arms, calling him, but when Dean's eyes flew open, they were still black. Disheartened, Sam looked up at Cas, almost missing as his brother opened his mouth and muttered: "Help me. Cas, help." One look at the pleading face and Castiel knew what he had to do.

"Sam, step back." With a frown, the hunter did as he was told, noticing the change in tone from the angel. This wasn't a request, this was an order. But he trusted Cas, especially after the little glimpse he'd had at the angels mind during their link. Still, he wondered what more he could do.

Castiel put both his hands on either side of Dean's face and closed his eyes in concentration. A slight tremble ran through his body and his face contorted in obvious pain. Then suddenly a blue light sprang to life in his palms, a dull glow at first, but soon it turned into a blinding bright radiance. Sam watched in awe as Castiel carefully controlled the white-blue light, letting it flow between his fingers before he redirected it towards Dean's head. The light hovered for a moment and then was absorbed through Dean's skin. The moment the light had completely disappeared, all hell broke loose.

Sam grabbed hold of his brothers twitching and convulsing body, while Castiel still had his head firmly in his hands. He muttered an incantation that Sam had never heard before, but the effect was impressive. Dean stilled instantly, went completely slack in Sam's hold as black smoke seemed to seep out of every pore on his body, rising up to form a ghostly body shape. It was similar to a demon cloud, but not quite as dense and black, more translucent. The cloud of smoke twitched and tried to return to the body below, but there was an invisible resistance. After several seconds, the smoke dissipated into thin air and it was over. Cas removed his hands and collapsed heavily next to Sam.

"Cas? What just happened? What was _that_?" Sam vaguely motioned with his hand towards where the black cloud had been just moments ago.

"I used my grace to expel the demonic portion within Dean's soul. That cloud was the essence of the demon he turned into. I could not do this without his consent; otherwise I would have expelled half of his soul as well. I had hoped he would have the strength to do it on his own, after we woke up his fighting instincts, but he was too weakened."

"So, it's gone? He's no longer a knight?"

"No. But he still is bearing the Mark of Cain. Removing his longing for the blade will take much longer. But with our help, he can do it."

xxx

"Gah!" Dean woke up with a splitting headache. Squeezing his eyes shut against the offending light, he tried to remember what the hell he had to drink last night to deserve this mother of all hangovers. Awareness slowly returning to his body, he noticed that he was lying on a hard surface, but his head was cushioned on something soft, warm and… moving?

"Hey, you with us again?"

Sam. Well, that explained the moving cushion, but he still had no clue how he had ended up there. The was no sound except some faint traffic noise and he decided to give his vision another chance. Maybe that would give him a clue. He carefully opened one of his eyes, squinting against the brightness that immediately made his headache flare up again. After a few blinks he recognized the face of his annoying little brother hovering a little too close for comfort above him.

"Sammy? W- what happn'd?" The tears in his brother's eyes confused him even more, little did he know that they were shed over the fact that his own eyes had turn back to their natural green color.

"Dean…" Was all his little brother said before he crushed him with his gigantic arms. Puzzled, Dean returned the hug. And that's when his memories decided to make their grand entrance. He groaned at the sharp pain in his head and at the vivid pictures that invaded his mind. After what felt like an eternity, he pushed back from the hold Sam still had on him, and looked at his brother with haunted expression.

"Sam…Cas…I…I'm…" But there were no words. Nothing could even begin to express how he felt, nothing could ever justify what he had done. He looked at them helplessly, before he lowered his gaze in shame.

"Dean, Crowley tricked you, he manipulated and used you. What you saw in our minds, that is who you really are, that is the man your brother and I were willing to risk everything for, just to get you back. There is no apology needed, my friend."

Unconvinced, Dean looked away, and of all places, his gaze fell onto the bloody blade, that was lying forgotten on the floor. Familiar feelings of warmth and power rose up and he tried to shake off the arms that were still supporting him.

Next thing he knew, he was flat on his back with Castiel holding both his arms down, face contorted in anger and determination.

"No! I did not give up my grace so you could just run back to that blade. You will learn to control your cravings, and you will never, ever touch that thing again, do you understand me?"

The passion and resentment behind each of these words shocked Dean into submission. He stared wide-eyed at the angel above him, all thought about the blade forgotten. He tried to comprehend what he thought he had just heard, but it seemed so impossible. Surely Castiel wouldn't – but deep down he knew that this was exactly the kind of stupid thing that Cas would do.

"You- you gave up your grace? For me? Cas…" He heard Sam gasp in the background, obviously equally as shocked by the latest turn of events.

Castiel's expression softened, as he watched Dean process the information. "It was my choice Dean. We were out of options, so I took the last chance I saw." He paused and looked Dean straight in the eyes. "You're worthy. Despite what you may think, I will never regret doing this."

Dean nodded weakly, but he felt a dark pit in his stomach. Again Cas had sacrificed everything for him. He wished the angel – no, he no longer was an angel, and whose fault was that again? – would stop doing this. He wasn't worth it. Dean's thoughts flashed back to what he had seen during the mind link. Sam and Cas both seemed to think of him as some kind of super hero, and not the utter and complete fuck up that he really was.

At the same time, he knew that he couldn't give in to the darkness and anger that threatened to reclaim him. Cas had given up his grace, willingly, to save him; he owed it to him to try his very best at fighting the influence of the mark. If Cas believed in him, and Sam believed in him, then maybe it was time to start to believe in himself?

* * *

_So this is it. There is a short and fluffy epilogue which will be posted tomorrow, to soften the blow that the finale will undoubtedly deal us all._

_As always, I hope you enjoyed this little story and I would love to hear your comments, criticism and generally all your theories on how the season finale will end! _


	6. Chapter 6

**AN:** I want to thank all of you for taking the time to read this story, to review, comment and share your own ideas and theories with me. I had a blast writing this and all the feedback really helped me to stay focused and motivated me to keep writing. A special thank you to all the guest reviewers, I can't reply to you via PM, but you are all awesome!

Enjoy this bit of tender feels before our hearts will be crushed to dust tonight!

**Warnings:** None, just fluffy brotherly love

* * *

Sam had gone to find them a car, now that angel transport was no longer available, while Cas and Dean cleaned up the apartment. They decided to take Cain's body with them, he might have been a demon, but he had also helped them and in their books, that meant he deserved at least a proper funeral.

The long drive back home to the bunker was spent largely silent, all three of them needing the time to sort through their thoughts and emotions and to rebuild walls that had come crashing down.

Cas eventually fell asleep on the back seat, his new humanity had left him physically and mentally drained. During a brief pit stop to fuel up, both Sam and Dean had left the car to stretch their legs. While Sam paid for the gas and the refreshments at the little store, Dean leant against the trunk of their car. It was an older model Toyota family van, and it stood for everything Dean hated in cars, but, according to Sam, the choice in NYC had been limited and this was the best he could find.

"Hey." Dean flinched at the words, and then he felt the car dip slightly as his brother leaned up against it next to him.

"Hey…" he paused, choosing his next words carefully. So far he had avoided all serious talk, but he knew that he needed to get a few things out in the open. "Look, I can't promise that I will suddenly be all touchy-feely and we share all our secrets. That's not us. But I will try to talk. Just not yet, okay?"

"That is all I ask. And it goes both ways. I know you're not ready to talk about what happened to you, but if you ever are, I'm here."

"Look, back there, Cas-" he swallowed hard, still having a hard time accepting his friend's sacrifice. "He opened a three way communication between us. I remember most of what you and Cas shared, but I don't know how much of my crap made it over to you?"

"Some of yours, some of Cas'. Not much though. Enough to understand."

Dean nodded, understanding all the things that Sam didn't say out loud. "So, where do we go from here? I mean, the blade, I…"

"I've been thinking about that." Dean rolled his eyes, yeah, what else did he expect? "Cas said he knows a place where we can safely hide that thing. Look, I'm not sayin' we give it up for good, but you need to learn to control the power first. Once we know more, once it's safe…" He didn't need to end that sentence. They both knew what a formidable weapon the blade was, if there was a way to use it safely, it would be worth the effort. "Cain, he uh, he told us a few things, but I haven't been able to confirm them yet… but I swear, I will find a way. Cas too. This time, you are not alone." Dean looked up and he saw sincerity radiate from his younger sibling. Giving Sam a short nod that said so much more than words could ever convey, he pushed himself off the car, snatched the bag of chips from Sam and walked over to the driver's side.

"I'll drive. Let's see what this piece of crap is really made of!" Sam smiled as he got in the passenger's seat, glad to see that their life was slowly getting back to normal.

xxx

Over the next week, things had progressed in a guarded, but positive way. Both brothers made an effort to communicate better, but there were long periods of silence in the bunker. Cas had left the brothers a few days after their return, saying that he needed to come to terms with his humanity. He promised to stay in touch and did so with daily phone calls to Dean. While upset with the former angel's decision, both hunters understood that he needed time alone to figure out what to do with his new, and this time most likely permanent, human life.

Dean was dealing with all that had happened to him and Sam understood that this was something his brother needed to do alone. He seemed more open towards Cas than him, which really was no surprise after all the tension of the last few months. In addition to that, the things Sam had glimpsed at during their link, the extent of the bond the angel shared with Dean, had surprised him.

So it came as a surprise to Sam when Dean came up to him one evening with two beers in hand and settled himself in the chair next to him. He silently handed him a beer, opened his own bottle and took a deep swig. Gaze focused on a spot on the floor, he asked softly:

"Does the craving ever go away?"

Sam had watched his brother with open curiosity, unsure what this was about, but sensed that it was a step in the right direction. And he knew exactly what Dean was talking about.

"No. It won't control your life any more, but it will always be there. Though, over time it will get easier to push it aside, easier to resist. It helps if you think about all the bad things the blade brought with it. That's what gets me through the bad times."

"'Gets'? You stopped five years ago, and still…?"

"Like I said, it never stops. Letting go, that was just the first step. Now comes the hard part. You need to learn to control the desire. It's tough and it's painful, and there will be times when you want nothing more than to go back to it. But I'm here and I'll have your back, same as you had mine."

Dean looked up at his brother. "Until I piss you off again."

"Dean…"

"No, let me finish. You've grown, Sam. And I don't mean your height. You've grown up and I sometimes fail to realize that. But no matter what you say, no matter how wise and old you get, you need to understand that you will always be my little brother. There is nothing, _nothing_ that will ever change that, and I will keep making crappy decisions to keep you alive. That's wired in too deep."

Sam nodded slowly at his brothers words. "I know. And I guess I have to figure out how to live with that. Because I really meant what I said, you need to respect my decisions. Even if you don't like them. But I think I understand you better now. When you were taken from me, that moment when your eyes turned black, I would have given anything to get you back."

"We're pretty screwed up, huh?"

Sam nodded sadly. "Yeah we are."

"I mean, any psychiatrist would have a field day with us: Codependent ex-addicts with low self esteem and violent tendencies…. Hell, they'd lock us up for life!"

"Probably should." Sam chuckled. "But you know, acknowledging that we have issues is the first step in the healing progress…"

"You really think we can ever be 'normal'?" Dean asked in disbelief

"Normal? No!" Sam snorted, genuine humor in his eyes. He looked over at Dean and his expression turned somber and sincere. "No I don't think that was ever really an option for us. But we could start with being brothers again? If you want."

Instead of an answer, Dean put his beer aside, got up and pulled his brother into a bone crushing hug, which was reciprocated just as enthusiastically by Sam. They'd been through hell, figuratively and literally, but what got them out of it was their bond as brothers. And in the end, that was all that counted.

* * *

_Edited after watching 9x23: HOLY CRAP! no words... Just wow. _


End file.
